Mouse adenovirus will be developed as a model system for molecular genetic studies of viral pathogenesis. The mechanisms by which the species-specific human adenoviruses cause disease are poorly understood, in part due to the lack of an animal model. The molecular biology of mouse adenovirus will be characterized in order to utilize an in vitro mutagenic approach to correlate gene functions with adenovirus pathogenesis. Molecular clones of mouse adenoviral DNA will be used to examine the expression of mouse adenoviral genes in infected mouse L cells. Viral RNAs will be characterized by hybridization analyses, and the RNA transcription map will be determined and compared to that of the human adenoviruses. This will allow rational design of mutagenic strategies to investigate viral genes in a transcription unit thought to be involved in pathogenesis. Initially, viral mutants will be isolated which lack a restriction enzyme site. These mutants, which will be likely to have deletion and/or substitution of nucleic acid sequences, will be characterized with respect to their properties in both cell culture and in vivo infections. As transcription map information becomes available, site-directed viral mutants will be constructed, by obtaining mutations in plasmid DNA and subsequent transfer of the mutations to viral DNA. Pathogenesis of wild-type and mutants of mouse adenovirus will be examined with respect to susceptibility of several inbred strains of mice and presence of virus and viral nucleic acids in various tissues of infected mice. Several human adenovirus genes, which are not required for viral growth in cell culture, have been postulated to be important in vivo in pathogenesis. Using the mouse adenovirus as a model, it should be possible to correlate the function of such genes with adenovirus pathogenesis. Thus, these molecular and biological studies will yield information on mechanisms by which adenoviruses cause disease.